Conveyor apparatus

ABSTRACT

A conveyor apparatus includes a pusher piece ( 19 ) fixed to a conveying rod ( 18 ) adapted to reciprocate along a board conveyance path, and a switching mechanism adapted to switch the pushing piece, by turning the conveying rod a predetermined angle, between an engaged position where the pusher piece ( 19 ) engages with a rear end face of a board ( 7 ) and a retracted position where the pusher piece ( 19 ) does not interfere with the board ( 7 ). The switching mechanism includes a guide member ( 23 ) provided with a guide hole ( 24 ) adapted to guide a guide rod ( 22 ). The guide hole ( 24 ) is made up of first and second guide holes ( 25  and  26 ) configured to extend in parallel to each other in a conveyance direction and slanted coupling guide holes ( 27, 27 ) adapted to couple ends of the first and second guide holes ( 25  and  26 ). When the conveying rod ( 18 ) reciprocates, the guide rod ( 22 ) makes a round of the closed-loop guide hole ( 24 ). When the guide rod ( 22 ) is guided by the first guide hole ( 25 ), the pusher piece ( 19 ) is positioned at the engaged position. When the guide rod ( 22 ) moves from the first guide hole ( 25 ) to the second guide hole ( 26 ), the conveying rod ( 18 ) axially rotates a predetermined angle, thereby positioning the pusher piece ( 19 ) at the retracted position.

The present application is a National Stage Application ofPCT/JP2012/071622, filed Aug. 27, 2012, which claims priority fromJapanese Patent Application No. 2011-185695, filed Aug. 29, 2011.

FIELD OF THE INVENTION

The present invention relates to a conveyor apparatus, which, forexample, is effectively used for a reflow soldering apparatus providedwith a decompression process for degassing a soldered portion duringsoldering.

BACKGROUND OF THE INVENTION

The reflow soldering apparatus solders, for example, a printed circuitboard on which electronic components have been mounted using creamsolder, solder paste, or the like while conveying the board on aconveyor, inside a furnace having a preheating process, a reflowprocess, and a cooling process in sequence (See Patent Document 1).

Patent Document 2 discloses a method for conveying a board in a reflowfurnace. A conveyor system disclosed in Patent Document 2 includes amain endless conveyor belt configured to extend from an inlet to anoutlet of a reflow furnace and operated at a constant speed. A boardconveyance path is formed to convey boards from the inlet to the outletof the reflow furnace on the main endless conveyor belt. On the boardconveyance path, plural pushers are placed, being spaced away from eachother in a workpiece conveyance direction, and each of the pushersreciprocates in directions the same as and opposite to the workpiececonveyance direction. The pusher can push the board on the main endlessconveyor belt upward and convey the board in the workpiece conveyancedirection at a controlled speed. An endless belt has been adopted toreciprocate the pushers attached to the endless belt. When the endlessbelt rotates in a forward direction, the pusher moves in the workpiececonveyance direction, and when the endless belt rotates in a reversedirection, the pusher moves in the direction opposite to the workpiececonveyance direction.

A first pushers included in the plural pushers is used to send a boardinto a reflow process of the reflow furnace. A second pushers are usedto send the board out of the reflow process and convey the board fromthe reflow process to a cooling process. The first and second pushersare controlled to move independently of the main endless conveyor beltat a speed faster than the main endless conveyor belt.

In soldering using a reflow furnace, preferably a degassing process isapplied in advance to avoid foaming in accompanying with heating. Forexample, in the reflow soldering apparatus shown in Patent Document 1,when a decompression chamber capable of reducing ambient pressure isinstalled on a board conveyance path such that a soldered portion formedon the board and molten by heating will be degassed in the decompressionchamber, a single conveyor (main endless conveyor belt) cannot beinstalled over the entire board conveyance path including thedecompression chamber because the decompression chamber needs to beenclosed hermetically during decompression. Therefore, separateconveyors are installed in the decompression chamber and in conveyancepaths in processes preceding and succeeding the decompression chamber.In this case, if a conveyor is installed in the decompression chamber,there is a problem in that mechanical components of the conveyor becomeexpensive to withstand a decompressed atmosphere and that maintenancefrequency is increased.

With the board conveyance method described in Patent Document 2, aircylinders are used to move the pushers up and down, resulting inincreased maintenance frequency. Also, the air cylinders themselves needto be moved in the conveyance direction.

Patent Document 1

Japanese Patent Laid-Open No. 2000-188467

Patent Document 2

Japanese Patent Laid-Open No. 11-40941

SUMMARY OF THE INVENTION

An object of the present invention is to provide a conveyor apparatuscapable of carrying a workpiece in and out of a desired process.

A further object of the present invention is to provide a conveyorapparatus which lends itself to easy maintenance as well.

A conveyor apparatus according to the present invention comprises: aconveying rod adapted to reciprocate along a conveyance path along whicha workpiece is conveyed; a pusher member fixed to the conveying rod andconfigured to protrude from the conveying rod; and a switching mechanismadapted to switch the pusher member, by turning the conveying rod apredetermined angle, between an engaged position where the pusher memberengages with the workpiece and a retracted position where the pushermember is separated from the workpiece.

The conveyor apparatus according to the present invention allows aworkpiece to be carried in and out of a desired process and lends itselfto easy maintenance as well. The conveyor apparatus according to thepresent invention is suitably applied to a reflow furnace.

According to a preferred embodiment of the present invention, theswitching mechanism includes a guide member related to the conveyingrod; the conveying rod includes a guided portion protruding from theconveying rod; the guide member includes a guiding portion adapted toguide the guided portion of the conveying rod; the guiding portion isconfigured to guide the guided portion into a closed loop using firstand second guiding portions configured to extend in parallel to eachother along the conveyance path and first and second coupling guideportions configured to couple ends of the first and second guidingportions to each other; the guide member is configured such that theguided portion makes a round of a guiding portion of the closed loop ofthe guide member through one reciprocating motion of the conveying rod;the pusher member of the conveying rod assumes the engaged position whenthe guided portion of the conveying rod moves forward by being guided bythe first guiding portion; and the pusher member of the conveying rodassumes the retracted position when the guided portion of the conveyingrod moves backward by being guided by the second guiding portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram showing a reflow solderingapparatus equipped with a conveyor apparatus according to an embodimentof the present invention;

FIGS. 2(A) to 2(D) are explanatory diagrams showing operation of theconveyor apparatus;

FIG. 3 is a sectional view showing the conveyor apparatus;

FIGS. 4( a) and 4(b) are plan views showing guide members, where FIG. 4(a) shows a guide member on the right side as viewed from an outlet sideto an inlet side of a furnace while FIG. 4( b) shows a guide member onthe left side;

FIG. 5 is a longitudinal section view showing a guide member; and

FIG. 6 is an overall configuration diagram of a reflow solderingapparatus equipped with a modification of a drive system for first andsecond conveying rods.

DESCRIPTION OF SYMBOLS

1 . . . Furnace; 2A, 2B . . . Preheating chamber; 3A, 3B . . . Reflowchamber; 4 . . . Cooling chamber; 5 . . . Decompression chamber; 5A . .. Upper housing; 5B . . . Lower housing; 6 . . . Partition wall; 7 . . .Printed board with electronic components mounted thereon; 8, 9, 10 . . .Board conveyance rail; 11 . . . Inlet; 12 . . . Outlet; 13 . . .Conveyor apparatus; 13A . . . First conveyance mechanism; 13B . . .Second conveyance mechanism; 14, 15, 16 . . . Heater; 17 . . . Coolingdevice; 18 . . . First conveying rod; 19 . . . Pusher piece; 20 . . .Rod support member; 20 a . . . Rod bearing hole; 20 b . . . Guidingportion; 21 . . . Support wall; 21 a . . . Guide groove; 22 . . . Guiderod; 23 . . . Guide member; 23 a . . . Guide member body; 24 . . . Guidehole; 25 . . . First guide hole; 26 . . . Second guide hole; 27 . . .Coupling guide hole; 28 . . . Blocking piece; 29 . . . Pivot pin; 30 . .. Linking piece; 31 . . . Return spring; 32 . . . Second conveying rod;33 . . . Upright member; 34 . . . Coupling rod; 35 . . . Chain conveyor;36 . . . Coupling rod

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention will be described belowwith reference to the accompanying drawings.

Overall Configuration of Reflow Furnace:

As shown in FIG. 1, a reflow soldering apparatus (reflow furnace)includes plural chambers partitioned in a workpiece conveyance directionand lined up in series within the furnace 1. Specifically, the reflowfurnace 1 includes, in order in the workpiece conveyance direction: twopreheating chambers 2A and 2B located on the right side of the drawing,two reflow chambers 3A and 3B located in the center of the drawing, andone cooling chamber 4 located on the left side of the drawing.Furthermore the reflow furnace 1 includes a decompression chamber 5 inthe reflow chamber 3B. Reference number 6 denotes a partition walladapted to partition adjacent chambers. An inert gas—nitrogen gasaccording to the present embodiment—is supplied as an ambient gas intothe reflow furnace 1 to prevent oxidation of solder.

A printed circuit board (hereinafter referred to simply as a “board”) 7with electronic components mounted thereon is conveyed on conveyancerails laid linearly in the reflow furnace 1. The conveyance rails aremade up of three pairs of rails 8, 9, and 10 which are arranged inseries in the workpiece conveyance direction, forming a pair of linearworkpiece conveyance paths by being placed in a same horizontal plane inthe reflow furnace 1. The first conveyance rails 8 are disposedhorizontally from a position in front of an inlet 11 of the furnace 1 toan inlet of the decompression chamber 5 in the furnace 1. The secondconveyance rails 9 are disposed horizontally in the decompressionchamber 5. The third conveyance rails 10 are disposed horizontally froman outlet of the decompression chamber 5 to an outlet 12 of the furnace1. The rails in each of the conveyance rail pairs 8, 9, and 10 areinstalled on right and left sides of the conveyance path of the board 7,supporting right and left edges of a bottom face of the board 7.

Cream solder has been applied to soldering locations on a top face ofthe board 7 which is input to the reflow furnace 1 and electroniccomponents have been put on the cream solder. The board 7 withelectronic components placed thereon via the cream solder are movedalong the conveyance rails 8, 9, and 10 by the conveyor apparatus 13.

That is, the board 7 is conveyed intermittently by the conveyorapparatus 13 from a position in front of the inlet 11 of the furnace 1.First, the board 7 is sent to the first preheating chamber 2A and heatedthere in a first preheating process for a predetermined period of timein an ambient gas heated by a heater 14. Next, the board 7 is sent tothe adjacent preheating chamber 2B next by the conveyor apparatus 13 andheated there in a preheating process for a predetermined period of timein an ambient gas heated by a heater 14. Next, the board 7 is sent tothe first-stage reflow chamber 3A by the conveyor apparatus 13, and asoldered portion is molten by being heated there in a reflow process fora predetermined period of time in an ambient gas heated by a heater 15.

The decompression chamber 5 in the second-stage reflow chamber 3B isdivided horizontally into an upper housing 5A and lower housing 5B, andthe lower housing 5B is fixedly placed in the reflow chamber 3B. Incontrast, the upper housing 5A is configured to be able to move up anddown by means of an actuator—specifically, a cylinder device (notshown)—and able to assume two states: a tightly closed state (seeFIG. 1) in which the upper housing 5A is placed in close contact withthe lower housing 5B by moving down and an open state (not shown) inwhich the upper housing 5A is placed above and spaced away from thelower housing 5B by moving up.

Thus, the board 7 is carried into the decompression chamber 5 in thereflow chamber 3B from the reflow chamber 3A by the conveyor apparatus13, in open state in which the upper housing 5A of the decompressionchamber 5 is placed above and spaced away from the lower housing 5B. Onthe other hand, the tightly closed state is achieved in a decompressionprocess in which the decompression chamber 5 is depressurized to degasthe cream solder on the board 7. In the decompression process, thesoldered portion is heated and degassed for a predetermined period oftime. That is, the soldered portion on the board 7 is heated and moltenin an ambient gas heated by a heater 16, the decompression chamber 5 issubsequently put in the tightly closed state and depressurized by avacuum pump (not shown) to a predetermined decompressed atmosphere inwhich the soldered portion is degassed, and the molten soldered portionon the board 7 is degassed in the predetermined decompressed atmosphere.

Subsequently, the decompression chamber 5 is put in the open state, theboard 7 is sent by the conveyor apparatus 13 to the cooling chamber 4through the reflow chamber 3B heated by the heater 15, and the solderedportion solidifies in the cooling process there by being cooled by acooling device 17 for a predetermined period of time. Then, the board 7is carried outside from the cooling chamber 4 through the outlet 12 ofthe furnace 1 by the conveyor apparatus 13.

Conveyor Apparatus 13:

Next, the conveyor apparatus 13 will be described below. The conveyorapparatus 13 includes a first conveyance mechanism 13A and secondconveyance mechanism 13B.

First, the first conveyance mechanism 13A will be described. The firstconveyance mechanism 13A includes first conveying rods 18 (FIGS. 1 and3). The first conveying rods 18 are placed horizontally along the firstconveyance rails 8, extending in the furnace 1 from a position in frontof the inlet 11 of the furnace 1 to a position in front of thedecompression chamber 5 (FIG. 3). Four pusher pieces 19 are positionedat intervals on the first conveying rod 18. The left and right pusherpieces 19 are fixedly attached to the respective first conveying rods18. As described later, as the first conveying rod 18 is axiallyrotated, each pusher piece 19 can assume an engaged position (positionindicated by a solid line in FIG. 3) where the pusher piece 19 abuts theboard 7 and a retracted position (position indicated by a virtual linein FIG. 3) spaced away from the board 7.

An end of each first conveying rod 18 on the side of the furnace inlet11 is inserted in a bearing hole 20 a of a rod support member 20. Thefirst conveying rod 18 is supported by the rod support member 20 axiallyrotatably, but immovably in an axial direction. The rod support member20 has a guiding portion 20 b on an outer surface. A support wall 21 iselected on an outer side of the rod support member 20. The guidingportion 20 b of the rod support member 20 is engaged with horizontalguide groove 21 a formed in an inner surface of the support wall 21. Therod support member 20 is configured to be able to move horizontally bybeing guided by the guide groove 21 a provided with one end and anotherend. Thus, the first conveying rod 18 can move horizontally in thefurnace 1 in a conveyance direction of the board 7 along with the rodsupport member 20.

When the first conveying rod 18 advances from the side of the inlet 11of the furnace 1 to the side of the outlet 12 (hereinafter referred toas “forward movement”), the pusher piece 19 (see FIG. 3) is positionedat a place (engaged position) where the pusher piece 19 engages with arear face of the board 7 on the conveyance rails 8, and when the firstconveying rod 18 advances from the side of the outlet 12 of the furnace1 to the side of the inlet 11 (hereinafter referred to as “backwardmovement”), the pusher piece 19 is positioned at a place (retractedposition) retracted to above the board 7. The pusher piece 19 isswitched between the engaged position and the retracted position byaxially rotating the first conveying rod 18 a predetermined angle.

Switching Mechanism for Switching Pusher Piece 19 Between EngagedPosition and Retracted Position:

The switching mechanism includes a guide rod 22 (see FIGS. 1 and 3)fixed in position to an end (front end) of the first conveying rod 18 onthe side of the furnace inlet 11. The guide rod 22 extends downward fromthe first conveying rod 18. The switching mechanism includes a guidemember 23 (see FIGS. 1 and 3 to 5) placed in connection with the guiderod 22 and placed below the guide rod 22. The guide member 23 has a body23 a which is a box-shaped member, and a guide hole 24 is formed in atop face of the box-shaped body 23 a. The guide rod 22 protruding fromthe first conveying rod 18 has its lower end inserted in the guide hole24.

FIGS. 4( a) and 4(b) are plan views showing the guide members 23, whereFIG. 4( a) shows the guide member on the right side as viewed from theoutlet side to the inlet side of the furnace while FIG. 4( b) shows theguide member on the left side. Referring to FIG. 4, the guide hole 24includes a first guide hole 25 adapted to place the pusher piece 19 ofthe first conveying rod 18 at the engaged position, a second guide hole26 adapted to place the pusher piece 19 at the retracted position, and acoupling guide hole 27 adapted to couple the two guide holes 25 and 26.The first guide hole 25 and second guide hole 26 extend linearly alongthe conveyance direction of the board 7. Also, the first and secondguide holes 25 and 26 extend in parallel to each other by being spacedaway from each other. Also, the first and second guide holes 25 and 26are joined together at both ends, i.e., at a front end and rear end inthe workpiece conveyance direction via the coupling guide holes 27described above.

Continuing to refer to FIG. 4, the rear end (end in upper part of FIG.4) of the first guide hole 25 is coupled to the rear end (end in upperpart FIG. 4) of the second guide hole 26 via a slant coupling guide hole27 extending linearly in a diagonal direction. On the other hand, afront end portion (end in lower part of FIG. 4) of the first guide hole25 is coupled to the front end (end in lower part of FIG. 4) of thesecond guide hole 26 via another slant coupling guide hole 27 extendinglinearly in a diagonal direction. In this way, the ends of the first andsecond guide holes 25 and 26 are coupled to each other via the couplingguide holes 27, forming the closed-loop guide hole 24, which inconjunction with the guide rod 22 inserted into the guide hole 24, makesup a cam mechanism adapted to swing the pusher piece 19 between theengaged position and the retracted position.

As described above, the pusher piece 19 assumes an engaged position andretracted position. The first guide hole 25 is a cam groove adapted toplace the pusher piece 19 at the engaged position. The board 7 locatedon rails has its rear end engaged with the pusher piece 19, and when thefirst conveying rod 18 moves forward, the board 7 is pushed by thepusher piece 19 and thereby conveyed from one processing position toanother processing position. When the conveyance is finished, the firstconveying rod 18 moves backward and returns to its original position.When the first conveying rod 18 moves backward, the pusher piece 19 ispositioned at the retracted position.

When the guide rod 22 is located in the first guide hole 25, the pusherpiece 19 assumes the engaged position. On the other hand, when the guiderod 22 is located in the second guide hole 26, the pusher piece 19assumes the retracted position. Therefore, with the first conveying rod18, when the guide rod 22 moves forward by being guided by the firstguide hole 25 (direction of arrow A in FIG. 4), the pusher piece 19 ispositioned at the engaged position (see FIG. 3) and moves the board 7forward by pushing the rear face of the board 7. On the other hand, withthe first conveying rod 18, when the guide rod 22 moves backward bybeing guided by the second guide hole 26 (direction of arrow B in FIG.4), the pusher piece 19 is positioned at the retracted position (seeFIG. 3) above the board 7 so as not to interfere with the board 7.

The following means is provided such that the guide rod 22 will moveforward by being guided by the first guide hole 25 during forwardmovement of the first conveying rod 18 and move backward by being guidedby the second guide hole 26 during backward movement of the firstconveying rod 18.

As shown in FIGS. 4 and 5, on a back face in upper part of the body 23 a(FIG. 5) of the guide member 23, blocking pieces 28 are placed atopposite ends of the closed-loop guide hole 24. One of the blockingpieces 28 is placed, intersecting the first guide hole 25 while theother blocking piece 28 is placed, intersecting the second guide hole26. Each of the blocking pieces 28 is fixed at one end to a pivot pin29. The pivot pin 29 is turnably installed between the first guide hole25 and second guide hole 26, perpendicularly penetrating the body 23 aof the guide member 23. A linking piece 30 is placed on a bottom face inlower part of the body 23 a of the guide member 23. The linking piece 30is fixed at one end to a lower end of the pivot pin 29 and fixed at theother end to one end of a return spring 31 made up of a tension spring.The return spring 31 is fixed at the other end to the lower part of thebody 23 a of the guide member 23.

As described above, the blocking piece 28 coupled with the linking piece30 via the pivot pin 29 is located at such a height position as tointerfere with the guide rod 22 while the linking piece 30 is located atsuch a height position as not to interfere with the guide rod 22.

Therefore, during forward movement of the first conveying rod 18, as theguide rod 22 moves forward and advances to the front end of the firstguide hole 25 by being guided by the first guide hole 25, the guide rod22 comes into contact with the first blocking piece 28 illustrated inlower part of FIG. 4. As the guide rod 22 further moves forward, thefirst blocking piece 28 turns against the spring force of the returnspring 31. Then, the guide rod 22 reaches the front end (end in lowerpart of FIG. 4) of the first guide hole 25. When the guide rod 22 passesthe first blocking piece 28, the blocking piece 28 is returned to itsoriginal position by the return spring 31. In a forward movement processof the first conveying rod 18, i.e., in the process of advancing to thebottom end illustrated in FIG. 4 by being guided by the first guide hole25, the pusher piece 19 is located at the engaged position (see FIG. 3)as described above. Therefore, the pusher piece 19 engages with theboard 7 and pushes the board 7 one process forward to an adjacent, nextprocess (e.g., from the reflow process to the decompression process).

Next during backward movement of the first conveying rod 18, as theguide rod 22 moves backward from the front end of the first guide hole25 (moves upward from the lower end of the first guide hole 25illustrated in FIG. 4) by being guided by the first guide hole 25, theguide rod 22 collides with the blocking piece 28 located across thefirst guide hole 25. As can be seen well from FIG. 4, the blocking piece28 diagonally crosses the first guide hole 25. Preferably, the blockingpiece 28 has an inclination angle equal to that of the coupling guidehole 27. In FIG. 4, when the guide rod 22 collides with the blockingpiece 28 by moving upward from the lower end of the first guide hole 25,the guide rod 22 enters the slant coupling guide hole 27 by being guidedby the slanted lateral edge of the blocking piece 28 and moves to thesecond guide hole 26 by passing through the coupling guide hole 27.

With the first conveying rod 18, when the guide rod 22 moves backward bybeing guided by the second guide hole 26, the guide rod 22 comes intocontact with the second blocking piece 28 illustrated in upper part ofFIG. 4. As the guide rod 22 further moves backward, the second blockingpiece 28 turns against the spring force of the return spring 31illustrated in the upper part of FIG. 4. Then, the guide rod 22 reachesan end of the second guide hole 26 (upper end of the second guide hole26 in FIG. 4). When the guide rod 22 passes the second blocking piece28, the blocking piece 28 is returned to its original position by thereturn spring 31. In a backward movement process of the first conveyingrod 18, i.e., in a process in which the first conveying rod 18 movesbackward by being guided by the second guide hole 26, the pusher piece19 is located at the retracted position (see FIG. 3) as described above.Therefore, being positioned at the retracted position above the board 7so as not to interfere with the board 7, the pusher piece 19 moves oneprocess backward.

Next, with the first conveying rod 18, when the guide rod 22 movesforward by being guided by the second guide hole 26, (moves downwardfrom the upper end of the second guide hole 26 in FIG. 4), the guide rod22 collides with the blocking piece 28 located across the second guidehole 26. As can be seen well from FIG. 4, the blocking piece 28illustrated in upper part of FIG. 4 diagonally crosses the second guidehole 26. Preferably, the blocking piece 28 has an inclination angleequal to that of the coupling guide hole 27. In FIG. 4, when the guiderod 22 collides with the blocking piece 28 by moving downward from theupper end of the second guide hole 26, the guide rod 22 enters the slantcoupling guide hole 27 by being guided by the slanted lateral edge ofthe blocking piece 28 and moves to the first guide hole 25 by passingthrough the coupling guide hole 27. That is, the guide rod 22 enters thecoupling guide hole 27 by being guided by the blocking piece 28 havingthe lateral edge slanted in the traveling direction of the guide rod 22.The coupling guide hole 27 is slanted in the traveling direction of theguide rod 22, and the guide rod 22 enters the first guide hole 25 bybeing guided by the slanted coupling guide hole 27. The operationdescribed above is repeated subsequently.

Thus, through one reciprocating motion (forward movement and backwardmovement) of the first conveying rod 18, the board 7 can be conveyed oneprocess forward, i.e., to the next process. Note that the slant couplingguide hole 27 may be straight as described above or may be curved tosome extent.

Note that the plural pusher pieces 19 for respective ones of pluralprocesses are fixed to the first conveying rod 18 (FIG. 2). This allowsthe boards 7 in respective processes to be sent to the next processesthrough a single forward motion of the first conveying rod 18. That is,by the first conveying rod 18, the board 7 located in front of the inlet11 of the reflow furnace 1 is conveyed to the first preheating chamber2A (preheating process), the board 7 located in the first preheatingchamber 2A is conveyed to the next preheating chamber 2B (preheatingprocess), the board 7 located in the preheating chamber 2B is conveyedto the reflow chamber 3A (reflow process), and the board 7 located inthe reflow chamber 3A is sent to the decompression chamber 5(decompression process).

Next, the second conveyance mechanism 13B will be described. The secondconveyance mechanism 13B has a configuration similar to that of thefirst conveyance mechanism 13A. That is, the second conveying rod 32(see FIG. 1) is placed horizontally, extending in the furnace 1 fromimmediately behind the decompression chamber 5 of the furnace 1 to aposition ahead of the outlet 12 of the furnace 1. Two pusher pieces 19are fixed to the second conveying rod 32 at a distance from each other.Each pusher piece 19 protrudes from the rod 32. As with the firstconveying rod 18, the second conveying rod 32 is supported by the rodsupport member 20 axially rotatably, but immovably in an axialdirection. The rod support member 20 is configured to be able to movehorizontally by being guided by the guide groove in the support wall.Thus, the second conveying rod 32 is also configured to be able to movehorizontally in the furnace 1 in a conveyance direction of the board 7along with the rod support member 20.

Using the same switching mechanism as the one installed on the firstconveying rod 18, the second conveying rod 32 is configured such thatthe pusher piece 19 is placed at such a position (engaged position) asto push the rear face of the board 7 on the conveyance rails 10 when thesecond conveying rod 32 advances (moves forward) from the side of theinlet 11 of the furnace 1 to the side of the outlet 12, and is placed ata position (retracted position) retracted to above the board 7 when thesecond conveying rod 32 moves backward from the side of the outlet 12 ofthe furnace 1 to the side of the inlet 11. Consequently, through onereciprocating motion (forward movement and backward movement) of thesecond conveying rod 32, the board 7 is conveyed one process forward,i.e., to the next process. Also, the plural pusher pieces 19 forrespective ones of plural processes are fixed to the second conveyingrod 32 as well, allowing the boards 7 in respective processes to be sentto the next processes. That is, by the second conveying rod 32, theboard 7 located in the decompression chamber 5 is sent to the coolingchamber 4 (cooling process) and the board 7 located in the coolingchamber 4 is sent outside through the outlet 12 of the furnace 1.

As shown in FIG. 3, a pair of the first conveying rod 18 and switchingmechanism is installed on both right and left sides of the conveyancepath so as to push the right and left ends of the board 7, the firstconveying rod 18 having the pusher piece 19, and upright members 33erected on top faces of the right and left rod support members 20 arecoupled by a coupling rod 34 so that the right and left first conveyingrods 18 will operate together. The second conveying rod 32 is configuredsimilarly.

Means for making the first conveying rod 18 and second conveying rod 32reciprocate (move forward and move backward) will be described next. Asshown in FIG. 1, a chain conveyor 35 is disposed outside the furnace 1on the side of the outlet 12. The chain conveyor 35 is placedhorizontally, parallel to the conveyance direction of the board 7. Therod support member 20 of the second conveying rod 32 is fixed to a chainportion of the chain conveyor 35. The rod support member 20 of the firstconveying rod 18 and rod support member 20 of the second conveying rod32 are coupled via a coupling rod 36. The coupling rod 36 penetrates thefurnace 1 and is placed outside the decompression chamber 5.

The first conveying rod 18 and second conveying rod 32 move apredetermined distance (equivalent to one process) forward when thechain conveyor 35 rotates a predetermined angle forward in the directionof arrow A in FIG. 4, and move a predetermined distance (equivalent toone process) backward when the chain conveyor 35 rotates a predeterminedangle backward in the direction of arrow B in FIG. 4. In this way, asthe chain conveyor 35 rotates a predetermined angle forward andbackward, the first conveying rod 18 and second conveying rod 32 isreciprocated a predetermined distance (equivalent to one process).

Operation of the conveyor apparatus 13 will be described below withreference to FIG. 2. FIG. 2(A) shows how the board 7 is placed in eachprocess and processed there for a predetermined period of time. FIGS.2(B) to 2(D) show how the board 7 is transferred to the next processafter being processed in the state of FIG. 2(A) for the predeterminedperiod of time.

In FIG. 2(C), the first conveying rod 18 and second conveying rod 32 arein states described below. That is, the pusher pieces 19 of the firstconveying rod 18 are at the engaged position, being located on theupstream side of the respective boards 7 located in the reflow chamber3A (reflow process), in the preheating chamber 2B (preheating process),in the preheating chamber 2A (preheating process), and in front of thefurnace 1 inlet, respectively. The pusher pieces 19 of the secondconveying rod 32 are at the engaged position, being located on theupstream side of the respective boards 7 in the decompression chamber 5(decompression process) and cooling chamber 4 (cooling process),respectively.

As the first conveying rod 18 and second conveying rod 32 move forwardafter the state of FIG. 2(C), with the guide rod 22 being guided by thefirst guide hole 25 as a result of forward rotation of the chainconveyor 35, the board 7 in each process is sent to the next step by thepusher piece 19 as shown in FIGS. 2(C) to 2(D).

That is, by the first conveying rod 18, the board 7 located in front ofthe inlet 11 of the furnace 1 is conveyed to the first preheatingchamber 2A (preheating process), the board 7 located in the firstpreheating chamber 2A is conveyed to the next preheating chamber 2B(preheating process), the board 7 located in the preheating chamber 2Bis conveyed to the reflow chamber 3A (reflow process), and the board 7located in the reflow chamber 3A is sent to the decompression chamber 5(decompression process). Also, by the second conveying rod 32, the board7 located in the decompression chamber 5 is sent to the cooling chamber4 (cooling process) and the board 7 located in the cooling chamber 4 issent outside through the outlet 12 of the furnace 1.

Next, as a result of backward rotation of the chain conveyor 35, thefirst conveying rod 18 and second conveying rod 32 are transferred fromthe state of FIG. 2(D) to the state of FIG. 2(A). That is, as the firstconveying rod 18 and second conveying rod 32 move backward, the guiderod 22 enters the second guide hole 26 by being guided by the couplingguide hole 27 and the pusher pieces 19 are placed at the retractedposition.

In FIG. 2(A), the first conveying rod 18 and second conveying rod 32 arein states described below. That is, the first conveying rod 18 andsecond conveying rod 32 are placed outside the decompression chamber 5,the pusher pieces 19 are at the retracted position, and the pusherpieces 19 at the heads of the rods 18 and 32 are placed on oppositesides of the decompression chamber 5. In this state, the boards 7 areprocessed in respective processes for a predetermined period of time.

After the boards 7 are processed in respective processes in the state ofFIG. 2(A) for the predetermined period of time, the first conveying rod18 and second conveying rod 32 move backward as a result of backwardrotation of the chain conveyor 35, shifting from the state of FIG. 2(A)to the state of FIG. 2(B). That is, with the guide rods 22 being guidedby the second guide holes 26 and with the pusher pieces 19 being placedat the retracted position, the first conveying rod 18 and secondconveying rod 32 move backward by approximately one process.

In FIG. 2(B), the first conveying rod 18 and second conveying rod 32 arein states described below. That is, the pusher pieces 19 of the firstconveying rod 18 are at the retracted position, being located on theupstream side of the respective boards 7 located in the reflow chamber3A (reflow process), in the preheating chamber 2B (preheating process),in the preheating chamber 2A (preheating process), and in front of thefurnace 1 inlet, respectively. The pusher pieces 19 of the secondconveying rod 32 are at the retracted position, being positioned on theupstream side (rear end) of the respective boards 7 located in thedecompression chamber 5 (decompression process) and cooling chamber 4(cooling process).

Next, as a result of forward rotation of the chain conveyor 35, thefirst conveying rod 18 and second conveying rod 32 are transferred fromthe state of FIG. 2(B) to the state of FIG. 2(C). That is, as the firstconveying rod 18 and second conveying rod 32 move forward, the guide rod22 enters the first guide hole 25 by being guided by the coupling guidehole 27, the pusher pieces 19 are placed at the engaged position,transferring the first conveying rod 18 and second conveying rod 32 tothe state of FIG. 2(C). Subsequently, the above-described operation isrepeated, beginning with the state of FIG. 2(C) described above.

In this way, through one reciprocating motion (forward movement andbackward movement) of the first conveying rod 18 and second conveyingrod 32, the boards 7 are sent to next processes, respectively, andprocessed in respective processes for a predetermined period of time.

Regarding the decompression process, the board 7 can be carried into thedecompression process by the first conveyance mechanism 13A and carriedout of the decompression process by the second conveyance mechanism 13B.

Therefore, the printed circuit board 7 on which electronic componentshave been mounted via cream solder is conveyed from a position in frontof the inlet 11 of the furnace 1 by the conveyor apparatus 13 goingthrough processes one by one including the decompression process in thereflow furnace 1, and processed in each process for a predeterminedperiod of time. Consequently, the board 7 on which the electroniccomponents have been soldered is carried out of the furnace 1 throughthe outlet 12 of the furnace 1.

Note that the operations of the first conveying rod 18 and secondconveying rod 32 are performed by controlling a driving motor of thechain conveyor 35 according to a predetermined sequence.

The first conveying rod 18 and second conveying rod 32 may be driven byrespective chain conveyors independent of each other. That is, althoughthe first conveying rod 18 and second conveying rod 32 are driven by thecommon chain conveyor 35 in the above embodiment, two chain conveyors 35may be installed to drive the first conveying rod 18 and secondconveying rod 32 separately as a modification (FIG. 6). According tothis modification, the first conveying rod 18 and second conveying rod32 are driven independently by separate chain conveyors 35, 35.

That is, as shown in FIG. 6, the rod support members 20 of the firstconveying rod 18 and second conveying rod 32 are separated instead ofbeing coupled via a coupling rod and the chain conveyor 35 adapted todrive the first conveying rod 18 is installed on the inlet side of thefurnace 1 while the chain conveyor 35 adapted to drive the secondconveying rod 32 is installed on the outlet side of the furnace 1. Thefirst conveying rod 18 and second conveying rod 32 are coupled to therespective chain conveyors 35 via the respective rod support members 20,which are fixed to the chain portions of the respective chain conveyors35, as with the above embodiment. The operations of the first conveyingrod 18 and second conveying rod 32 are the same as those described withreference to FIGS. 2(A) to 2(D).

Although an example of guiding the guide rod 22 using the guide hole 24has been described in the above embodiment, this is not restrictive, andthe guide rod 22 may be configured to be guided, for example, by a guidegroove.

Although in the above embodiment, the first conveyance mechanism 13A hasa pair of the first conveying rods 18 and the second conveyancemechanism 13B has a pair of second conveying rods 32, each of theconveyance mechanisms may be configured to have a single conveying rod.

Although the common chain conveyor 35 is used in the above embodiment asdriving means adapted to reciprocate the first conveying rod 18 andsecond conveying rod 32, this is not restrictive, and a belt conveyor orthe like may be used alternatively. Of course, the first and secondconveying rods 18 and 32 may be driven by separate belt conveyors.

Although an example in which the decompression chamber is installed inthe reflow chamber has been described in the above embodiment, thedecompression chamber may be installed independently of the reflowchamber, or installed on the board conveyance path.

Also, although nitrogen gas is used as a furnace gas in the aboveembodiment, the gas is not limited to nitrogen gas. For example air maybe used.

What is claimed is:
 1. A conveyor comprising: a conveying rod adapted toreciprocate along a conveyance path along which a workpiece is conveyed;a pusher member fixed to the conveying rod and configured to protrudefrom the conveying rod; and a switching mechanism adapted to switch thepusher member, by turning the conveying rod a predetermined angle,between an engaged position where the pusher member engages with theworkpiece and a retracted position where the pusher member is separatedfrom the workpiece, wherein the switching mechanism includes a guidemember related to the conveying rod; the conveying rod includes a guidedportion protruding from the conveying rod; the guide member includes aguiding portion adapted to guide the guided portion of the conveyingrod; the guiding portion is configured to guide the guided portion intoa closed loop using first and second guiding portions configured toextend in parallel to each other along the conveyance path and first andsecond coupling guide portions configured to couple ends of the firstand second guiding portions to each other; the guide member isconfigured such that the guided portion makes a round of a guidingportion of the closed loop of the guide member through one reciprocatingmotion of the conveying rod; the pusher member of the conveying rodassumes the engaged position when the guided portion of the conveyingrod moves forward by being guided by the first guiding portion; and thepusher member of the conveying rod assumes the retracted position whenthe guided portion of the conveying rod moves backward by being guidedby the second guiding portion.
 2. The conveyor apparatus according toclaim 1, wherein the guiding portion of the closed loop and the guidedportion of the conveying rod make up a cam mechanism adapted to switchthe pusher member between the engaged position and the retractedposition.
 3. The conveyor apparatus according to claim 2, wherein theguiding portion of the closed loop is made up of a guide hole or a guidegroove.
 4. The conveyor apparatus according to claim 3, wherein: one endof the first guiding portion is coupled to one end of the first couplingguide portion; another end of the first coupling guide portion iscoupled to one end of the second guiding portion; another end of thesecond guiding portion is coupled to one end of the second couplingguide portion; and another end of the second coupling guide portion iscoupled to another end of the first guiding portion.
 5. The conveyorapparatus according to claim 4, wherein: a first blocking piece isplaced in a portion where the one end of the first guiding portion andthe one end of the first coupling guide portion are joined together; asecond blocking piece is placed in a portion where the other end of thesecond guiding portion and the one end of the second coupling guideportion are joined together; the first blocking piece has a function topermit the guided portion to move forward to the one end of the firstguiding portion by being guided by the first guiding portion and afunction to lead the guided portion to the first coupling guide portionwhen the guided portion moves backward from the one end of the firstguiding portion; and the second blocking piece has a function to permitthe guided portion to move backward to the other end of the secondguiding portion by being guided by the second guiding portion and afunction to lead the guided portion to the second coupling guide portionwhen the guided portion moves forward from a rear end of the secondguiding portion.
 6. The conveyor apparatus according to claim 1, whereinthe conveyance path is a board conveyance path of a reflow furnace.